Magnetostrictive linear actuators are well known in the art; finding extensive use in sonar applications, and more recently with deformable mirrors in advanced high energy laser systems. These actuators utilize the unique properties of a select group of magnetostrictive materials whose dimensions change as a function of the intensity of an applied magnetic field. To generate linear displacements, a cylindrical rod of magnetostrictive material is located within an electrical coil. Current flow through the coil produces a magnetic induction or flux density within the rod, resulting in a change in length of the rod proportional to the magnitude of the applied field.
Most magnetostrictive materials, however, display severe hysteresis in the relationship between the applied magnetic field and the magnetostrictive displacement. Consequently, the utility of magnetostrictive devices is limited in those applications where precise control of the displacement of the actuator is required. The prior art linear magnetostrictive actuators have been capable only of open loop operation. Consequently, there still remains a significant positional error.